In a transmission of a vehicular engine or the like, generally speaking, shift forks borne on a shift fork shaft in a manner to slide axially thereof are desired partly to supply a sufficient amount of lubricating oil between the forked pawl portions formed at the leading ends thereof and shift gears engaging with the pawl portions irrespective of the positions of shift forks on the shift fork shaft thereby to ensure smooth rotations of the shift gears, partly to supply a sufficient amount of lubricating oil between the shift fork shaft and the bearing portions of the shift forks thereby to ensure smooth and light sliding motions of the shift forks to the right or left, and partly to accurately move in parallel on the shift fork shaft at all times, whereby the operations of the transmission and the gear changing operations may always be conducted properly and efficiently as a whole.